1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to synchronizing beacon transmission for a set of femtocells.
2. Introduction
A wireless communication network may be deployed over a defined geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, access points (e.g., each supporting one or more macro cells) are distributed throughout a macro network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the network.
As the demand for high-rate and multimedia data services rapidly grows, there lies a challenge to implement efficient and robust communication systems with enhanced performance. To supplement conventional network access points (e.g., macro access points), small-coverage access points (e.g., with transmit power of 20 dBm or less) may be deployed to provide more robust coverage for access terminals. For example, a small-coverage access point installed in a user's home or in an enterprise environment (e.g., commercial buildings) may provide voice and high speed data service for access terminals supporting cellular radio communication (e.g. CDMA, WCDMA, UMTS, LTE, etc.).
In some cases, small-coverage access points may be referred to as, for example, femtocells, femto access points, home NodeBs, home eNodeBs, access point base stations, picocells, etc. Typically, such small-coverage access points are connected to the Internet and the mobile operator's network via a DSL router, a cable modem, or some other suitable means of connectivity. For convenience, small-coverage access points may be referred to as femtocells or femto access points in the discussion that follows.
In practice, macrocells are typically deployed on multiple frequencies. Due to scarcity of spectrum resources, femtocells often share the frequency channels used by the macrocells or are deployed on adjacent frequency channels. To attract the macrocell users idling on the macrocell frequencies to the femtocell frequency, a femtocell radiates beacon signals (e.g., comprising pilot, paging, and synchronization channels) on the macrocell frequencies. Information included in the beacon signal (e.g., control channel overhead messages) will enable an access terminal that is idling on the macrocell frequency to be redirected to the femtocell frequency. However, these beacon signal transmissions by the femtocell may create interference on the macro network that can affect the voice call quality of users receiving active service on the macrocell frequency and, in some cases, lead to call drops.
To limit this interference, the femtocells may transmit beacon signals in a periodic manner. However, this present a challenge to ensure that access terminals moving throughout coverage areas provided by femtocells will be able to quickly acquire the beacon signals transmitted by the femtocells.